In the latest snapshot 14w04b when placing a map in an item frame, it enlarges the item frame like normal, but the map will be invisible, leaving you with a large item frame but with no visible map in it. Also, blocks don't appear to be in the correct orientation/position or rendered correctly when placed in item frames, and they appear to be only half showing. And when I loaded up my world in this snapshot, all of my item frames that I had previously placed in the previous snapshot and were fine; flew off the wall, though I think that is because they have a new redstone ability so the game was "updating" them, albeit in a strange way. Nevertheless, they are not working correctly with maps or most items.